Glass reinforced plastic article



United States Patent 1 2,360,109 10/ 1944 Converse Mark E. Kelly, Jr. Midland, Michigan 697,594

Jan. 15, 1968 1 Nov. 24, 1970 A.0. Smith Corporation Milwaukee, Wisconsin a corporation of New York Inventor Appl. No. File'd Patented Assignee GLASS REINFORCED PLASTIC ARTICLE 1 6 Claims, 2 Drawing-Figs.

us. cl. 138/141, 138/153: 156/622, 156/172, 156/330 int. Cl. F161 9/16 Field of Search 138/153,

174, 145, 172, 141, 144, glass fiber digest; 264/209; 156/330, 62.2, i72gfd References Cited UNITED sTATEs' PATENTS 2,391,468 12/1945 Long 138/145X 2,467,999 4/1949 Stephens 138/ l 74X 2,653,887 9/1953 Slayter 138/145X 2,816,322 12/1957 Bjorksten 264/209 2,884,010 4/1959 Fischer..... 138/144 3,002,534 10/1961 Noland 156/172X 3,212,529 10/1965' Ullman et a1. 138/141 3,414,460 12/1968 Hassert et al. 156/172X Primary Examiner-Samuel Rothberg Assistant Examiner-Henry K. Artis Attorneys-Andrus and Starke, Merle E. Sceales and Howard .1 Barnett ABSTRACT: The invention relates to a glass reinforced plastic pipe having improved chemical resistance and including an inner layer of haphazardly arranged glass fibers impregnated with an epoxide resin with the glass of the inner layer containing a high proportion of alkali metal oxides. Surrounding the inner layer is an outer layer formed of helically wound glass fibers bonded with an epoxide resin and the glass of the outer layer contains a high proportion of aluminum 01tide.

Patented Nov. 24, 1970 INVENTOR. Mark E. Kelly JR.

BY $0 M Attorneys though the'amount of.

. l GLASS REI NE O R CED PLASTICARTICLE Fiber reinforcedplastie pipe is generally fabricated by winding strands ofjglass fibers about a mandrel and bonding the fibers-together with a thermosetting resin such as an epoxide v resin. .Where th'e conventional pipe isexposed in service to acids or strong alkaline materials,- it. has been found that the pipe is readily attacked by the chemicals so that failure results ina relatively sliortperiod of service. It has been discovered that failure is not due to the attack 'onithe resin. but instead, is

to be used in chemicalservice may consist of aninner liner consisting of glass mat impregnated-with resin, with the resin consisting of-about 90 percent by weightof the inner layer.

I Appliedto the outer surface of the inner layer isaseries of layers of helicallywound, substantially continuous glass fibers .impregnated with resin which provide thenecessary. strength for the tubulararticle. lflevertheless, the conventional plastic pipeutilizing the resin-rich inner layerhas drawbacks in that the inner layer lacks adequate reinforcement which may detractfrorn -the physicalbperformanceof the pipe. and even glass. fiber reinforcement in the inner layer is minimized, it is none the less subject to chernical attack. The present invention is directed to a. glass reinforced plastic article having improved chemical resistance.

FIG. 1 isa perspective view of. the reinforced tubular member. of the invention and FIG. 2 is across sectionof the tubular member illustrated in FIG; I. t 1 t The article comprises an inner ..layer 1 formed of haphazardly arranged glass fibersbonded with' an epoxide resin, and the glass of the inner layer 1 contains ahighperccntage of alkali metal oxides. Surrounding the inner layer 1 is an purer layer 2formed of helically wound glass fibers bonded with an-epoxide resin and the glass of the outer layer 2has a high percentage ofaluminum .oxideqThe tubular member prepared in accordance with the inventionhas marked improvement in chemical resistance over conventional glass reinforced plastic articles.

Theinnerlayerl'of the pipe is composed of haphazardly arranged fibers in the formof matting or the like, which are formed of a glass known inthetrade as Cv glass having the following generai formulation:

Percent SiOg .60-67 A120 2-8 03- 1-8 NafO+K 8-16 Mg0+ CaO 5-20 A specificillustration of a'glass composition falling within the above range is as follows in weight percent:

,The glass of the inner layer 1 is impregnatedwith the epox ide resin by conventional techniqueslln some cases theglass rnat may be preimpregnated .with the uncured resin, while in Process for Manufacture of-eCilycidylithers of Polyhydric Phenols." The epoxide resins are generally prepared by heating the polyhydricphenol with the halolhydrin a: atemperature in the range of 50 to 150C. and using l to 2 orniore mols of thehalohydrin per mol of the polyhydric phenol. An alkaline material," such as sodium or potassium hydroxide. is used in a stoichiometric excess of about 2 to 5 percent to the halohydrin. The heating is continued forseveral hours to effect the reaction andthe product is then washed free of salt and base. The product is not a single s irnple compound but is generally a complex mixture of glycidyl polyetliers and the principal product may be represented by the formula Awhere n is an integer of the series 0, l ,2,3 and R represents I the polyvalent hydrocarbon radical of the polyhydric phenol.

' The epoxide resins usedin the inyention normally have an epoxy equiva'leney greatcrthan 2. By-theepoxy equivalency is meant'the avera ge number of epoxy groups contained in the average molecule ofthe glycidyl ether. v

. The curing agents used to cure the epoxide resin to its infusible, rigid state may take the form 'of 4, 4 methylene dianjline, ethylenediamine, metaphenylene diamine, triethylene triamine, diaminofdiphenyl sulfone, acid .anhydrides such as phthaliqdodecenyl, succinic and chlorendicanhydrides and thelike.

The glass mat comprises from 5 to 50 percent by weight of t the combined weight of the glass mat and, resin in the inner layer and preferably about 5 to 15 percent. y

The glass mat for the inner layer 1 generally has a thickness in the range of 15 to 25.nrils as applied to the mandrel, and this layer will generally compress to a final linerthickness of about 3 .l 010 15 mils after application of the outer helical windings wound glass to be applied=depends on the strength required SK) A1363 5. 8 B 0 3. 6. Ntl O-l-Kfi) 12. 0 Mg0+ CaQ. l6. 1

and the ultimate use of the article. The glass of the outer layer 2 is a form' of glass referred to as S glass in the trade and has'the following general c ornposition in weight percent:

Percent P Si0z 60-67 A1203 I 20-30 a0 0-3 B 0 0-2. MgO 5-12 TiOz -1, Nil/ 0 l- K30 0-1 A specificillustrate of 'an.S glass formulation falling withiri the aboverange is as follows inweight percent:

an epoxide resin sirnilarto that used to impregnate theinn'er layers of thepipe. Theglass fibers generally comprise about 50 to percent by. weight of the combined weight of the glass fibers and resin in theouter layers and preferably about 60 to" 70 percent.

. thickness. If the glass mat is not impregnated with resin, the

resin is than applied over the glass mat and worked into the fibers. Following this, the helical windings of the S glass fibers forming layer 2 are applied over the glass mat and the glass fibers can be impregnated with the resin by any desired method, such as passing the fibers through a resin bath, brushing, dipping or spraying. After the desired number of layers of the S glass have been wound over the inner layer 1 of glass mat, the article is heated to a temperature generally in the range of 200 to 350F. for a period of time sufficient to cure or polymerize the epoxide resin, thereby resulting in an integrally bonded structure.

The following table illustrates the hoop tensile strength retention of various glass fiber reinforced plastic pipes when exposed to various alkali and acidic materials at elevated temperatures. Sample I is formed according to the invention and consists of an inner layer ofC glass mat having a compressed thickness of about l2 mils and a glass-to-resin ratio of l to 5, and an outer layer 2 of helical windings of S glass, both of which were impregnated with an epoxide resin.

Sample ll in the following table is a tubular article formed solely of helical windings of S glass fibers bonded with an epoxide resin, while Sample [11 is a tubular article formed with an inner layer ofC glass mat having a compressed thickness of about l2 mils and a glass-to-resin ratio of l to 5, and an outer layer of helically wound C glass fibers, both of which are bonded with an epoxide resin. Sample IV is a tubular article formed solely of helically wound C glass fibers bonded with an epoxide resin.

invention can be utilized to form a laminated article of any desired configuration and has particular application for a laminated article adapted to be exposed in service to chemical solutions or agents.

Various modes of carrying out the invention are contemplated as being within the scope of the following claims particularly pointing out and distinctly claiming the subject matter which is regarded as the invention.

lclaim: I

1. A reinforced article adapted to be exposed in service to chemical solutions, comprising a first layer composed of haphazardly arranged glass fibers impregnated with an epoxide resin, said glass fibers formed of a glass having the following composition in weight percent:

S Percent 1 2 60-67 A1 03 2-8 B20 1-8 Na O+K20 8-16 Mg0+ CaO -20 and a second layer composed of substantially continuous glass fibers circumferentially disposed around the inner layer and impregnated with an epoxide resin, said substantially continuous fibers being formed of a glass having the following composition in weight percent:

Percent SiO 60-67 A1 0 -30 CaO 0-3 B 0 0-2 MgO 5-12 TiO 0-1 Nflzo'i K20 I-Ioop tensile strength retention, percent Sample I Sample II Sample III Sample IV Tomp.,

Solution F 1 mo. 4 mo. 1 m0. 4 mo. 1 m0. 4 mo. 1 m0. 4 m0.

IIn, 10.5% 205 120. 0 118. 9 77. 5 69. 0 38. 3 33. 7 55. 6 43. 6 Ha, 36.5%-- 205 109. 3 91. 0 53. 0 37. 7 58. 5 46. 1 50. 7 31. 6 205 113. 1 110. 7 72. 5 64. 3 35. 3 26. 5 47. 8 38. 1

Water 205 113. 5 110. 9 70. 3 67. 3 36. 9 32. 6 32. 8 29. 3

From the foregoing Table, it can be seen that the tubular ar- 2. The article of claim 1 wherein said article is tubular in tide. Sample p pa n ccordanc with the invention. shape and said first layer comprises an annular liner and said had a hoop strength retention after a 1 month period which was substantially higher in all cases than the hoop tensile strength of the identical control sample which was not exposed to the solution and considered for comparative purposes to be I00 percent. Moreover, the retained hoop tensile strength of Sample I after 4 months of exposure was, in most cases, higher than that of the control sample. In contrast to this, the hoop tensile strength retention of Samples ll, Ill and IV was, in all cases, less than that of the control sample and substantially below the hoop tensile strength retention of Sampic I for the corresponding solutions.

The S glass. which contains a high percentage of aluminum oxide. is considered in the art tobe a relatively chemical resistant type of glass having substantially greater resistance to chemical attack than C glass used for the inner layer 1. However. the invention shows that utilizing the C glass inner layer, even though C glass is recognized as being less chemical resistant than 5 glass. produces a very substantial improvement in the overall chemical resistance of the tubular article. This is completely unobvious. for it would normally be expected that a pipe formed solely of a known chemical resistant type of glass. such as Sample ll in the foregoing table. would be more resistant to chemical attack than one having an inner liner ofa glass which is not particularly resistant to chemical attack.

While the above description has been directed to the fabrication of a pipe or tubular article. it is contemplated that the second layer comprises an annular section disposed around said liner.

3. The structure of claim 2, wherein said haphazardly arranged fibers are in the form of matting and the continuous fibers are helically arranged in a series of superimposed layers with each alternate layer having the opposite helix angle.

4. The structure of claim 1, wherein the glass fibers in the inner layer comprise from 5 to 50 percent by weight of said inner layer and the glass fibers in said outer layer comprise from 50 to percent of the weight ofsaid outer layer.

5. The structure of claim 1 wherein the inner layer has a thickness in the range of 15 to 25 mils.

6. A glass reinforced tubular article adapted to be exposed in service to chemical agents, comprising an inner layer composed of glass matting impregnated with a cured epoxide resin, said glass fibers having the following composition in weight percent:

Percent SiO 60-67 A1 0 2-8 203 1"8 N320 K20 MgO Ca() 5-20 and an outer layer composed of substantially continuous glass fibers helically wound around the inner layer and impregnated with cured epoxide resin, said substantially continuous glass fibers having the following composition in weight percent:

Percent SiO, 6067 A1203 -30 

